Vaccines are useful to immunize individuals against target antigens such as pathogen antigens or antigens associated with cells involved in human diseases. Antigens associated with cells involved in human diseases include cancer-associated tumor antigens and antigens associated with cells involved in autoimmune diseases.
In designing such vaccines, it has been recognized that vaccines which produce the target antigen in the cell of the vaccinated individual are effective in inducing the cellular arm of the immune system. Specifically, live attenuated vaccines, recombinant vaccines which use avirulent vectors, and DNA vaccines all lead to the production of antigens in the cell of the vaccinated individual which results in induction of the cellular arm of the immune system. On the other hand, sub-unit vaccines which comprise only proteins and killed or inactivated vaccines, which do induce a humoral response, do not induce good cellular immune responses.
A cellular immune response is often necessary to provide protection against pathogen infection and to provide effective immune-mediated therapy for treatment of pathogen infection, cancer or autoimmune diseases. Accordingly, vaccines which produce the target antigen in the cells of the vaccinated individual, such as live attenuated vaccines, recombinant vaccines which use avirulent vectors and DNA vaccines, are preferred.
While some vaccines have been reported effective in immunizing individuals prophylactically or therapeutically against pathogen infection or human diseases, there is a need for improved vaccines. There is a need for compositions and methods which produce an enhanced immune response.
Immune responses are also involved in rejection of cells, tissues, and organs and in graft versus host disease experienced by transplant patients. Often, the donor cells, tissues and organs have different subtype(s) of major histocompatibility complex class I (MHC I) antigens than that of the cells of the recipient. The recipient's immune system detects the difference in MHC I subtype and directs an immune response against the donor cells, tissues and organs.
Similarly, in patients receiving bone marrow transplants, differences in subtypes of MHC II antigens can result in rejection of the donor cells that express MHC II antigens.
There is a need for compositions and methods which can prevent or reduce the severity of transplant rejection.